Measuring the electric-hearing abilities of deaf infants and toddlers who use cochlear implants may lead to better outcomes for this population. Early-age cochlear implantation is becoming the standard of care to ' treat deafness as newborn hearing screenings become universal. While electric-hearing children reliably develop speech and language, they are still hearing impaired and exhibit degraded speech reception, music reception, and speech production compared to normal-hearing children. Current understanding of electric- hearing development, however, is limited, and methods to objectively measure auditory perception in electric-hearing infants and toddlers are few. The work proposed here measures detection abilities and reaction times in electric-hearing infants and toddlers. Detection is essential for speech discrimination, language comprehension and speech production. Reaction time has been demonstrated in normal hearing infants to correlate with sound level, and in adults to correlate with both sound level and perceived loudness. The objective of this application is to apply an established observer-based procedure, typically used to assess the auditory capabilities of normal-hearing infants, to measure detection ability and reaction time in electric- hearing infants and toddlers. Three specific aims are proposed. First, the ability to detect electrical stimulation at a level that typically occurs in response to conversational speech, will be measured. Second, the change in detection ability as a function of electrical level, as well as the minimum level that elicits reliable detection, will both be measured. Third, the dependence of reaction time on electrical stimulation level will be measured. Preliminary data indicate that meaningful information about detection and about reaction time can be measured from electric-hearing infants and toddlers using observer-based methods. Findings from this study will contribute to our understanding of how electric-hearing children perceive sound. This research program will inform studies measuring more complex perceptual abilities in electric-hearing infants and toddlers. Knowledge gained from these studies could permit improvements in clinical fitting and advance cochlear implant technology. [unreadable] [unreadable] [unreadable]